USBL/INS Tightly-Coupled Integration Technique for Underwater Vehicles

Abstract

This paper presents a new Ultra-Short Baseline (USBL) tightly-coupled integration technique to enhance error estimation in low-cost strapdown Inertial Navigation Systems (INSs) with application to underwater vehicles. In the proposed strategy the acoustic array spatial information is directly exploited resorting to the Extended Kalman Filter implemented in a direct feedback structure. The determination and stochastic characterization of the round trip travel time are obtained resorting to pulse detection matched filters of acoustic signals modulated using spread-spectrum Code Division Multiple Access (CDMA). The performance of the overall navigation system is assessed in simulation and compared with a conventional loosely-coupled solution that consists of solving separately the triangulation and sensor fusion problems. From the simulation results it can be concluded that the proposed technique enhances the position, orientation, and sensors biases estimates accuracy.

Position USBL/DVL sensor-based navigation filter in the presence of unknown ocean currents

“…Although the observability of the LTV system (13) has been established, it does not mean that the original nonlinear system (6) is also observable, and neither means that an observer for (13) is also an observer for (6). This however turns out to be true, as it is shown in the next theorem.…”

“…The first design linearizes the nonlinear range and RDOA measurements about the filter estimates in order to compute a suboptimal Kalman gain. In the latter, the feedback is accomplished by means of a precomputed transponder position fix from the USBL that resorts to a planar-wave approximation, previously used by the authors [6]. The Root-Mean-Square (RMS) of the steady-state position error of the three filters is presented in Table I.…”

“…The computation of this position fix often resorts to a Planar-Wave approximation of the acoustic wave arriving at the receiving array, previously used by the authors [6]. In that case, the error cannot be guaranteed to converge to zero due to the planar-wave approximation.…”

“…Traditional solutions resort either to the well known Extended Kalman Filter (EKF) [6], Particle Filters (PF) [3], which lack global asymptotic stability properties, or to filtering solutions that use a precomputed position fix from the USBL device using the range and bearing and elevation angles of the transponder. The computation of this position fix often resorts to a Planar-Wave approximation of the acoustic wave arriving at the receiving array, previously used by the authors [6].…”

Geometric bounding techniques for underwater localization using range-only sensors

“…Acoustic baseline navigation encompasses a number of techniques in which acoustic transponders are used to provide positioning information for underwater vehicles. The most common strategies for acoustic baseline navigation are Long Baseline (LBL) in which a number of acoustic beacons are deployed on the sea floor and localisation is achieved through triangulation like methods [2,3,4], Short Baseline (SBL), in which transponders are mounted on a supporting ship [5], and UltraShort Baseline (USBL), in which transponder elements are closely spaced in a single housing and are used for range-and-bearings localisation [6]. Each of these techniques requires significant effort in calibration, either in surveying the position of deployed acoustic beacons in LBL positioning or in calibration and alignment of SBL or USBL systems [7].…”